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  3. Grape Pests

Grape-Mealybug

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Gill's mealybug (Ferrisia gilli)

Grape mealybug (Pseudococcus maritimus)

Vine mealybug (Planococcus ficus)

Pest description and crop damage Mealybugs can be problematic in all three PNW states. However, mealybugs are only problematic for southern and eastern grape-growing regions of Oregon. Mealybugs may infest grape clusters resulting in direct crop losses. Grapes grown in Oregon's Willamette Valley have not been found to have cluster contamination by mealybugs. Vine and Gill's mealybug have recently been found in southern Oregon.

Mealybugs have soft, oval, flattened, distinctly segmented bodies. The size and shape varies with the species. Grape mealybug is the most prevalent vineyard mealybug in the PNW. The grape mealybug female adult is 0.25 to 0.5 inch long, pink to dark purple, and with a white, mealy, wax secretion. Long posterior filaments along the lateral margin of the body become progressively shorter toward the head. Eggs are yellow to orange and laid in cottony egg sacs. Crawlers that hatch from them are tiny (0.06 to 0.12 inch long), yellow to brown. Males and females are similar in early instar stages. Males pass through three nymphal instars, then form a cottony cocoon about 0.12 inch long in which the pupa is formed. All stages of the female are similar, varying in size only. The crawler stage of this pest is most mobile.

Mealybugs contaminate fruit with cottony egg clusters, eggs, immature stages, adults, and honeydew. Sooty mold (a black fungus) may grow on the honeydew. Most concerning is that grape and vine mealybugs may vector (spread) grapevine leafroll virus. These insects can spread the virus within and between regions and across vineyards. The virus may reduce crop yields and fruit quality. For this reason, it is important that growers know the status of mealybug presence in their vineyards.

Biology and life history Mealybug species vary in their life cycles. Mealybugs overwinter under loose bark, with the grape mealybugs overwintering on the cordons or upper parts of the vine structure; Gill's and vine mealybug overwintering under loose bark and the trunk down to the soil. As the mealybug populations increase in spring and summer, they move from bark to new growth to feed. Eggs can be laid on all plant parts during the season. Gill's mealybug lays live nymphs rather than eggs. As populations build, migrating mealybug populations may move to clusters during mid-late summer, causing direct crop damage. Most late summer populations return to old wood to overwinter.

Gill's and grape mealybugs are not as prolific in spreading as vine mealybugs. There are many host plants that may harbor both vine and Gill's mealybug. Grape mealybug has one to two generations per season; Gill's mealybug has one to three generations per season; and vine mealybug, which has not yet become established in the PNW, has 1-10 generations per year, depending on climate, with more generations in hotter climates. To learn more about the different mealybug species, see

Mealybugs in Vineyards: Identifying, Monitoring, and Managing https://ucanr.edu/sites/CentralSierraAg/files/332945.pdf and

Pest Alert: Gill's Mealybug https://www.oregon.gov/ODA/shared/Documents/Publications/IPPM/GillsMealy....

Sampling and thresholds Control thresholds have not been defined. The number of late-season migrating mealybugs increase the likelihood of contamination with vine leafroll virus and warrant control. Commercial pheromone traps are available to aid in effective monitoring for grape and vine mealybugs. Vineyards with known virus infection, particularly grapevine leafroll disease (GLD), should be monitored for the presence of mealybug populations using pheromone traps starting during the late dormant period.

Management-biological control

Little research has been done in the PNW on the effectiveness of natural enemies in keeping mealybug populations at levels below economic damage. Parasitic wasps, predatory bugs, predatory beetles, lacewings, and spiders can take a considerable toll of mealybugs in vineyards that use few broad-spectrum chemicals. A lady beetle, the "mealybug destroyer" (Cryptolaemus montrouzieri), is considered an effective predator of mealybugs worldwide. It has been seen in recent seasons in some Washington vineyards and is available for release from some insectaries.

Management-cultural control

To prevent movement and spread of mealybugs and virus within and between vineyards, it is critical to restrict movement of fruit and manage winery pomace (grape waste) properly.

Management-chemical control: HOME USE

  • Dormant-season spray
  • superior-type oil
  • Growing-season spray (Control is most effective when mealybugs are in the crawler stage)
  • acetamiprid
  • cyfluthrin
  • pyrethrins (often used in a mix with other ingredients)-Some formulations are OMRI-listed for organic use.

Management-chemical control: COMMERCIAL USE

Dormant season

A dormant spray with horticultural oil and/or the use of buprofezin (Applaud) causes the least disruption to other insects and the integrated pest management program. Control is most effective when mealybugs are in the crawler stage, and Applaud is the recommended treatment. Direct spray the trunk, canes, or cordons using sufficient water to loosen bark and drive the pesticide into cracks. If infestations are patchy, use spot-treat only. Frequent use of imidacloprid or chlorpyrifos can result in spider mite outbreaks.

Early season

  • buprofezin (Applaud) at 0.40 to 0.53 lb ai/A. PHI 7 days. Apply at early stages of crawler emergence by ground using 50 to 200 gal/A water, depending on the size of the grape plants/canopy. Use of a higher volume of water will ensure better coverage, especially under adverse conditions such as hot, dry weather and/or a dense canopy. Do not exceed 1.05 lb ai/A per season. Allow at least 14 days between applications. Group 16 insecticide.
  • Chromobacterium subtsugae strain PRAA4 (Grandevo) at 0.6 to 0.9 lb ai/A (2 to 3 lb product per acre). PHI 0 days. OMRI-listed for organic use. See label for details on tank mixing with other products. Group UNB Bacterial Agent insecticide.
  • imidacloprid (Admire Pro and other brands)
    • Soil application at 0.25 to 0.5 lb ai/A. PHI 30 days. Apply in one or two drip irrigations between budbreak and pea-size stage of berry development. Consult label for restrictions. Do not apply more than 0.5 lb ai/A per year. Group 4A insecticide.
    • Foliar application at 0.036 to 0.05 lb ai/A. PHI 0 days. Do not exceed 0.1 lb ai/A per year. Allow 14 days between applications. Group 4 A insecticide.
  • phosmet (Imidan 70W) at 1.0 to 1.5 lb ai/A. PHI 7-14 days depending on timing of application; see label. When appliedas a delayed dormant (pre-budbreak) spray with a spreader sticker. REI 14 days. Do not use more than 4.55 lb ai/A each year. Phosmet has not shown good control in Oregon. Use is not allowed during grapevine dormancy. This is an organophosphate insecticide and use should be limited. Group 1B insecticide.
  • spirotetramat (Movento) at 0.10 to 0.13 lb ai/A. PHI 7 days. Ensure that there is adequate foliage for absorption of the compound. Allow 30 days between applications. Do not exceed 0.2 lb ai/A per season. A high-quality spreader should be used to enhance penetration into foliage; see label for more details on which adjuvants to use or avoid. Group 23 insecticide.

Summer

  • buprofezin (Applaud) at 0.40 to 0.53 lb ai/A. PHI 7 days. Do not exceed 1.05 lb ai/A per season. Allow at least 14 days between applications. Apply by ground applicator using a minimum of 50 gal/A water, depending on grapevine size. Using a higher volume of water assures better coverage, especially under adverse conditions such as hot, dry weather and/or a dense canopy. Do not exceed two applications per crop cycle. Group 16 insecticide.
  • Chromobacterium subtsugae strain PRAA4 (Grandevo) at 0.6 to 0.9 lb ai/A (2 to 3 lb product per acre). PHI 0 days. OMRI-listed for organic use. See label for details on tank mixing with other products. Group UNB Bacterial Agent insecticide.
  • imidacloprid (Admire Pro and other brands) at 0.036 to 0.05 lb ai/A. Foliar application. PHI 0 days. Do not exceed 0.1 lb ai/A per year. Allow 14 days between applications. Group 4 A insecticide.
  • malathion (Malathion 5 EC) up to 0.94 lb ai/A. PHI 3 days. Make summer application at first sign of honeydew on fruit (early to mid-July). Malathion has not shown good control in Oregon. Group 1B insecticide. This is an organophosphate insecticide. Toxic to bees and most aquatic invertebrates, and carries the risk of mammalian toxicity. Do not apply when bees are foraging.
  • phosmet (Imidan 70-W) at 1.0 lb ai/A applied when fruit sizing and pest is present on fruit and/or leaves. Ensure adequate coverage of fruit and leaves for best result. PHI 7 days. REI 14 days. Do not apply more than 4.55 lb ai/A annually. Supplemental label (FIFRA 2(ee) for WA. Group 1B insecticide. This is an organophosphate insecticide and use should be limited. Phosmet has not shown good control in Oregon.
  • spirotetramat (Movento) at 0.10 to 0.13 lb ai/A. PHI 7 days. Ensure that there is adequate foliage for absorption of the compound. Allow 30 days between applications. Do not exceed 0.2 lb ai/A per season. A quality spreader should be used to enhance penetration into foliage; see label for more details on which adjuvants to use or avoid. Do not exceed 0.2 lb ai/A per season. Group 23 insecticide.
  • thiamethoxam + chlorantraniliprole (Voliam Flexi) at 0.054 lb ai/A. PHI 14 days. Allow 14 days between applications. Do not apply more than 0.109 lb ai/A of thiamethoxam or 0.2 lb ai/A of chlorantraniliprole per season (2 applications) per season. Groups 4A and 28 insecticides.

For more information:

Prevention and Management of Grapevine Leafroll Virus and Mealybugs in Oregon Vineyards (https://catalog.extension.oregonstate.edu/em8990)

Distribution and Monitoring of Grape Mealybug: A Key Vector of Grapevine Leafroll Disease in Oregon (https://catalog.extension.oregonstate.edu/em9092)

Field Monitoring for Grapevine Leafroll Virus and Mealybug in Pacific Northwest Vineyards (https://catalog.extension.oregonstate.edu/em8985)